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The rate of reaction between two reactants A and B decreases by a factor of 4 if the concentration of reactant B is doubled. The order of this reaction with respect to reactant B is:[2005]
  • a)
    2
  • b)
    -2
  • c)
    1
  • d)
    -1
Correct answer is option 'B'. Can you explain this answer?
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The rate of reaction between two reactants A and B decreases by a fact...
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The rate of reaction between two reactants A and B decreases by a fact...
Understanding the Reaction Rate
The rate of a chemical reaction can be expressed using the rate law, which is determined by the concentrations of the reactants and their respective orders. For a reaction involving reactants A and B, the rate can be represented as:
Rate = k [A]^m [B]^n
Where:
- k = rate constant
- [A] = concentration of reactant A
- [B] = concentration of reactant B
- m = order with respect to A
- n = order with respect to B
Effect of Doubling Concentration
According to the problem, when the concentration of B is doubled, the rate of reaction decreases by a factor of 4. This means:
New Rate = Rate / 4 when [B] is changed to 2[B]
Mathematical Representation
Let’s set the original rate when [B] is at its original concentration:
Original Rate = k [A]^m [B]^n
When the concentration of B is doubled, the new rate will be:
New Rate = k [A]^m (2[B])^n = k [A]^m (2^n [B]^n) = 2^n * k [A]^m [B]^n
Setting these equal according to the problem:
2^n * (Original Rate) = (Original Rate) / 4
Solving for n
Cancelling the original rate from both sides, we get:
2^n = 1/4
This can be rewritten as:
2^n = 2^(-2)
Thus, n = -2.
Conclusion
The order of the reaction with respect to reactant B is -2, indicating that increasing the concentration of B leads to a significant decrease in the reaction rate. Hence, the correct answer is option 'b) -2'.
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Community Answer
The rate of reaction between two reactants A and B decreases by a fact...
Yes B is correct
here is simple trick
rate of reaction is decreasing thus ans will be in - ve . now,
w.r.t. B -
if conc. of B is double the rate of reaction becomes 4 (means 2 times)
thus ans. is -2
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Read the passage given below and answer the following questions:The rate of a reaction, which may also be called its velocity or speed, can be defined with relation to the concentration of any of the reacting substances, or to that of any product of the reaction. If the species chosen is a reactant which has a concentration c at time t the rate is - dc/dt, while the rate with reference to a product having a concentration x at time t is dx/dt. Any concentration units may be used for expressing the rate; thus, if moles per liter are employed for concentration and seconds for the time, the units for the rate are moles litre–1sec–1. For gas reactions pressure units are sometimes used in place of concentrations, so that legitimate units for the rate would be (mm. Hg) sec–1 and atm. sec–1 The order of a reaction concerns the dependence of the rate upon the concentrations of reacting substances; thus, if the rate is found experimentally to be proportional to the ath power of the concentration of one of the reactants A, to the both power of the concentration of a second reactant B, and so forth, via., rate = k CAα CAβ the over-all order of the reaction is simply n = α + β + ----- (2) Such a reaction is said to be of the αth order with respect to the substance A, the βth order with respect to B.In the following questions, a statement of Assertion followed by a statement of Reason is given. Choose the correct answer out of the following choices on the basis of the above passage.Assertion: For a reaction: P + 2Q → Products, Rate = k [P]1/2[Q]1 so the order of reaction is 1.5Reason: Order of reaction is the sum of stoichiometric coefficients of the reactants.

Read the passage given below and answer the following questions:The rate of a reaction, which may also be called its velocity or speed, can be defined with relation to the concentration of any of the reacting substances, or to that of any product of the reaction. If the species chosen is a reactant which has a concentration c at time t the rate is - dc/dt, while the rate with reference to a product having a concentration x at time t is dx/dt. Any concentration units may be used for expressing the rate; thus, if moles per liter are employed for concentration and seconds for the time, the units for the rate are moles litre–1sec–1. For gas reactions pressure units are sometimes used in place of concentrations, so that legitimate units for the rate would be (mm. Hg) sec–1 and atm. sec–1 The order of a reaction concerns the dependence of the rate upon the concentrations of reacting substances; thus, if the rate is found experimentally to be proportional to the ath power of the concentration of one of the reactants A, to the both power of the concentration of a second reactant B, and so forth, via., rate = k CAα CAβ the over-all order of the reaction is simply n = α + β + ----- (2) Such a reaction is said to be of the αth order with respect to the substance A, the βth order with respect to B.In the following questions, a statement of Assertion followed by a statement of Reason is given. Choose the correct answer out of the following choices on the basis of the above passage.Assertion: Reactions can occur at different speeds.Reason: Rate of reaction is also called speed of reaction.

The rate of reaction between two reactants A and B decreases by a factor of 4 if the concentration of reactant B is doubled. The order of this reaction with respect to reactant B is:[2005]a)2b)-2c)1d)-1Correct answer is option 'B'. Can you explain this answer?
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